Giant font atlas handing

[YukinoHayakawa]

The font worked well until I try to bake thousands of (Asian characters) moderately big characters (32 pixels) into the atlas. With Vulkan the texture is stretched vertically so it renders garbage. With DX11 it fails when creating the texture. Using RenderDoc I noticed that the texture is 1024*32768 in size, while my GPU has texture dimension limit of 16384. It astonished me when I found this line in the source: https://github.com/vurtun/nuklear/blob/0275cc578981ab9cebd79e4245a8322087d2b518/nuklear.h#L12688 It might be better if the user can specify the width in font config or guess from font size.

Another problem caused by this width "calculation" is that much space is wasted in the lower half of the texture.

[YukinoHayakawa]

I edited the source to guess a width based on the largest font size. It works and memory utilization seems better but still might not suit general cases (and it uses ceil from std lib). Better ideas?

int max_size = 0;
if (!image_memory || !width || !height || !config_list || !count) return nk_false;
for (config_iter = config_list; config_iter; config_iter = config_iter->next) {
    it = config_iter;
    do {range_count = nk_range_count(it->range);
        total_range_count += range_count;
        total_glyph_count += nk_range_glyph_count(it->range, range_count);
        if(it->size > max_size)
            max_size = (int)ceil(it->size);
    } while ((it = it->n) != config_iter);
}
/* setup font baker from temporary memory */
for (config_iter = config_list; config_iter; config_iter = config_iter->next) {
    it = config_iter;
    do {if (!nk_tt_InitFont(&baker->build[i++].info, (const unsigned char*)it->ttf_blob, 0))
        return nk_false;
    } while ((it = it->n) != config_iter);
}
*height = 0;
*width = nk_round_up_pow2((int)sqrt(max_size * max_size * total_glyph_count));

[kphillisjr]

I agree that there is definitely an Implementation bug with the texture atlas when you take into account additional languages. As far as the effected rendering systems I can confirm this will effect all 3D API's since by the specification the texture sizes can be different.

• Direct3D 11 Device Limits - With the feature Levels specification this has a large variety of Maximum texture size Limits. ( See: https://docs.microsoft.com/en-us/windows/desktop/direct3d11/overviews-direct3d-11-resources-limits ). Just a quick list of different texture sizes is listed below...

  • Feature Level 9_1 - 2048 by 2048 textures
  • Feature Level 9_2 - 2048 by 2048 textures
  • Feature Level 9_3 - 4096 by 4096 Textures
  • Feature Level 10_0 - 8192 by 8192 Textures
  • Feature Level 11_0 - 16384 by 16384 textures.

• DirectX 10 - The minimum Max Texture requirement for this is 8192 by 8192 pixels as per the Resource Limits documentation ( see: https://docs.microsoft.com/en-us/windows/desktop/direct3d10/d3d10-graphics-programming-guide-resources-limits )

• DirectX 9 Hardware Differences. ( This needs Confirmation, but I'm certain this is accurate. )

  • Shader Model 1.0 - This needs Confirmation, but I believe the value is 1024 pixels by 1024 pixels.
  • Shader Model 2.0 - 2048 by 2048 pixel textures - This is
  • Shader Model 3.0 - This raises the Limit to 4096 by 4096.

• OpenGL Specifications ( uses: GL_MAX_TEXTURE_SIZE )

  • OpenGL 1.3 - 64 by 64 Pixels ( See Page 235, Table 6.27 - Implementation Dependent Values ).
  • OpenGL 2.0 - 64 by 64 pixels ( see Page 293, Table 6.32 - Implementation dependent values ).
  • OpenGL 2.1 - No change, See page 298, Table 6.33 - Implementation Dependent Values.
  • OpenGL 3.0 - Minim size of Maximum Texture size is 1024 by 1024 (See page 386, table 6.46 - Implementation dependent values )
  • OpenGL 4.0 ( core ) - No change, See page 363, Table 6.41 - Implementation Dependent Values.
  • OpenGL ES Specifications
  • OpenGL ES 1.0, and 1.1 - No minimum value is specified in the OpenGL ES 1.0/1.1 specifications, but the OpenGL 1.3 Specification clearly stated a minimum of 64 by 64 pixels.
  • OpenGL ES 2.0 - 64 by 64 pixels. ( Page 152, table 6.18 )
  • OpenGL ES 3.0 - 2048 by 2048 pixels ( Page 273, Table 6.28 ).

• Vulkan - The Minimum value for the Maximum Texture size is 4096. ( See the Required Limits table under the "Features, limits, and formats" chapter/section.

Note: In practice OpenGL Implementations can safely handle 2048 by 2048 pixels textures. The only case I know of where the limit is 1024px by 1024px is the Windows GDI driver for OpenGL which is limited to OpenGL Version 1.1.

Edit Fixed grammar and minor facts.

[YukinoHayakawa]

@kphillisjr Very useful summary of texture limits. I think this shows that the user definitely should have control over the texture size.

[IvanFedotovIvanFedotov]

Hello! We use your library to draw texts in a rectangles. The range of letters in the text is 2 languages ​​(Russian and English) and several letter sizes. For large letter sizes, the output texture begins to exceed the size of 512 * 32768 pixels. Both ranges with several letter sizes go in one atlas. Tell me please, is there any way or example how to solve this problem? Is another option also possible? Add functionality to your code so that the user can set the size of the atlas texture to the width. Different from 512 pixels?